"We will use this period of time to evaluate all additional information which becomes available," Blackstone said in a statement. According to several published reports, Blackstone has about $550 million invested with the fund.

Outside investors typically had to wait a year to get all their money back since SAC only allows investors to take 25% of their capital out of the fund each quarter. Because of that, only $660 million will leave the fund at the end of the quarter.

It's still not clear whether Morgan Stanley(MS) chose to keep its $180 million with SAC. Morgan Stanley is one of five so-called prime brokers that provide SAC with lucrative support services.

Morgan Stanley did not return calls for comment, and the SAC spokesperson would not discuss client decisions.